The present invention relates to casters, and more particularly to improvements in those portions of casters which support the wheel or wheels and enable the wheel or wheels to swivel about a substantially vertical axis, for example, relative to the leg of a piece of furniture, relative to the leg of a hospital bed or the like. Still more particularly, the invention relates to improvements in casters wherein the wheel or wheels are mounted between, and are rotatable relative to, prongs which are connected to each other by a substantially vertical web.
In many conventional casters, the wheel or wheels are rotatably mounted in a one-piece bifurcated frame having a pair of spaced-apart prongs and a vertically extending web which is integral with the prongs to form therewith a substantially U-shaped body. Such frames can be produced by deep drawing. Except in those instances when the caster is a so-called box runner or fix caster, the web of the U-shaped frame can constitute a component part of the swivel bearing which connects the caster to a leg or the like so that the frame and the wheel therein can swivel about an axis which extends at right angles to the axis of the wheel. To this end, the web of the frame can be provided with one or more circular tracks for balls or otherwise configurated rolling elements of one or more antifriction bearings which are interposed between the web and the supporting leg. The thus deformed web cooperates with a similar component at the lower end of the leg to form therewith a pair of races for one or more annuli of rolling elements. Alternatively, the web of the U-shaped frame which rotatably supports one or more rollers can be provided with a ring-shaped housing for one or more antifriction bearings surrounding a customary kingbolt extending upwardly beyond the bearing and being affixed to the leg of a piece of furniture or the like.
A drawback of frames which define tracks for rolling elements is that they must be made of an expensive material which is capable of being shaped in a deep drawing machine. The web deforming operation to provide therein one or more tracks for rolling elements is an expensive and time-consuming procedure. The situation is aggravated if the frame must be made of stainless steel or an equivalent high-quality material which presents additional problems in connection with the deformation of the web.
In accordance with a further earlier proposal, the prongs of the U-shaped frame forming part of a caster are integrally connected to each other by a substantially semicircular web or bridge which is welded to a bearing eye. Such solution is not entirely satisfactory because it is not possible to preassemble all component parts of the caster except by utilizing specially designed holding means which must be applied and remain applied until after the establishment of a connection between the prongs and the semicircular web.